Efficiency of conversion of food to wool in selected and unselected Merino types

Abstract

Comparisons were made between Collinsville, Bungaree, and Peppin Merino ewes in efficiency of conversion of food to wool. The effect of selection for some characters on efficiency of conversion within the Peppin Merino was also investigated.

The Collinsville ewes grew 14% more wool and had an 8% lower food intake at maintenance than did the Peppins. Differences in wool growth between the Peppin and Collinsville types fed ad lib. were mainly due to efficiency and body weight differences. Efficiency, intake, and body weight each had a similar influence on wool growth differences between Peppins and Bungarees.

Peppin ewes selected for wool production, either alone or together with crimp frequency, had a higher gross efficiency than unselected sheep fed below maintenance (13 and 8%) or ad lib. (14 and 13%). The efficiency difference between selected and unselected sheep increased, then decreased, with increasing intake. The decrease in efficiency differences at higher intakes did not appear to influence the ranking of selected or unselected sheep.

The response to selection for clean fleece weight was shown to develop a plateau after about one generation of selection. Selection had resulted in the elimination of a relationship between efficiency and wool growth. The present results indicate that further progress in fleece weight is unlikely to be made either by selecting for fleece weight with some control on fibre diameter or by selecting for increased surface area.